Synthesis of magnetic-responsive imidazole-based poly (ionic liquid)s as a recycle adsorbent for simultaneously removing iodine molecules and iodide ions

Abstract

Nuclear waste management and nuclear energy generation require the proper disposal of 129I and 131I, which are radioactive isotopes of iodine. For recognition of different types’ iodine, a magnetic poly (ionic liquid)s (Fe3O4@SiO2-MPS-PILs) was formed by the selected imidazole ionic liquid monomer and core–shell Fe3O4@SiO2-MPS via free radical polymerization. The resulting adsorbent containing plenty of imidazole N-heterocycle units, benzene rings, and ionic bonds in the backbones was suitable for simultaneously adsorbing iodine molecules and iodide ions. The adsorption mechanisms for iodine in cyclohexane and iodide ions from aqueous solution were based on charge transfer and ion exchange mechanisms, respectively. The adsorption equilibrium for iodine in cyclohexane was attained at 12 h, and the kinetics of iodine adsorption closely followed the pseudo-second-order model. Iodine adsorption on Fe3O4@SiO2-MPS-PILs was best described by Langmuir model with a maximum iodine adsorption capacity of approximately 714.29 mg g−1. Iodide ions adsorption was best explained with Freundlich model and a maximum adsorption capacity of 335.80 mg g−1 was achieved in an iodide solution with a 500 mg L–1 concentration. Notably, Fe3O4@SiO2-MPS-PILs retained over 90 % of its original adsorption performance after the 5th cycle. This work proves that the adsorbent Fe3O4@SiO2-MPS-PILs was efficient and recyclable, and has good application prospects in the practical treatment of iodine and iodide.